Hey, we are making a robot at school.Since we are 17 year old electronic student we don't know much about mechanics and stuff.We are making a robot controlled by micro controller and rs232 trough the internet.We want to let it drive on tracks. Easyest would be if we could get motors that work on 5volts and only use about 20mA.What would you suggest on using (what sort of motors) and do you know some stores where we can buy this.

Yea, you should never power a motor directly from a microcontroller (it will fry the microcontroller). The microcontroller just outputs a signal, then you must use that signal as an on/off switch to a much larger power source.

You also cant use it to control a relay, as a relay is high current too.

i think this store http://www.conrad.com/ should be able to help you out, you can pick your country when you get there and then look at the "model"(not sure on the english) making section for all kinds of little wheels and things... also motors... cogs or gears too

this place http://www.farnell.nl (or .com, and pick a flag) has more advanced stuff, relays, controllers and everything, but they suck for motors

Its a 1:24 scale tank (they have others as well, seeing as you are from europe you might be interested in the Leopard?). So it will have a complete chassis, body, motors, tracks, wheels, etc. all in a nice little package for US $89.99. Realistically, you could simply hack the remote and you'd be good to go, but that might take too much of the fun out of it.

Personally I'd scrap most internal electronics to get rid of the stupid toyish stuff (recoling action, digital firing sounds), throw a web cam on it and go.

You should try making your own tracks . Use a strip of wetsuit material the right width and cut diagonally from one corner of each end to about four centimetres down the opposite side. do a mirror image on the other end, then glue it together with an appropriate glue.

Ive never used wetsuit material. In the past i have made tracks from cloth. the thing to watch is that cloth stretches in different angles so you need to layer it to try countering the stretch. Also its easy to put grommets in the cloth for better traction.

we would like to use some cheap positioning servos for arms and stuff, 90° and 180° and they are 3.5kg/cm, the cost about 7 eurois that powerfull enough

we also need some continious rotation servos (2) for the the wheels, with tracks, where we can mount cogg wheels on

the main frame of the motor is about 15cm long and 10cm widei think in the end it will be about 25-30cm high and will way about 4 to 5kgmaybe this can give a better idea how strong the servos need to be

also one thing, the servos for the wheels need to be 100% the same torque and speed, otherwise the robot wont be able to drive 100% straight

edit: thanks for the reply's we are currently using the tracks from some kind of meccano toy box and are building the frame with that, works quit wellmaybe in a further stage we could use better materials